8 research outputs found
Polarization-Resolved Extreme-Ultraviolet Second-Harmonic Generation From Linbo3
Second harmonic generation (SHG) spectroscopy ubiquitously enables the investigation of surface chemistry, interfacial chemistry, as well as symmetry properties in solids. Polarization-resolved SHG spectroscopy in the visible to infrared regime is regularly used to investigate electronic and magnetic order through their angular anisotropies within the crystal structure. However, the increasing complexity of novel materials and emerging phenomena hampers the interpretation of experiments solely based on the investigation of hybridized valence states. Here, polarization-resolved SHG in the extreme ultraviolet (XUV-SHG) is demonstrated for the first time, enabling element-resolved angular anisotropy investigations. In noncentrosymmetric LiNbO3, elemental contributions by lithium and niobium are clearly distinguished by energy dependent XUV-SHG measurements. This element-resolved and symmetry-sensitive experiment suggests that the displacement of Li ions in LiNbO3, which is known to lead to ferroelectricity, is accompanied by distortions to the Nb ion environment that breaks the inversion symmetry of the NbO6 octahedron as well. Our simulations show that the measured second harmonic spectrum is consistent with Li ion displacements from the centrosymmetric position while the Nb─O bonds are elongated and contracted by displacements of the O atoms. In addition, the polarization-resolved measurement of XUV-SHG shows excellent agreement with numerical predictions based on dipole-induced SHG commonly used in the optical wavelengths. Our result constitutes the first verification of the dipole-based SHG model in the XUV regime. The findings of this work pave the way for future angle and time-resolved XUV-SHG studies with elemental specificity in condensed matter systems
Polarization-Resolved Extreme Ultraviolet Second Harmonic Generation from LiNbO
Second harmonic generation (SHG) spectroscopy ubiquitously enables the
investigation of surface chemistry, interfacial chemistry as well as symmetry
properties in solids. Polarization-resolved SHG spectroscopy in the visible to
infrared regime is regularly used to investigate electronic and magnetic orders
through their angular anisotropies within the crystal structure. However, the
increasing complexity of novel materials and emerging phenomena hamper the
interpretation of experiments solely based on the investigation of hybridized
valence states. Here, polarization-resolved SHG in the extreme ultraviolet
(XUV-SHG) is demonstrated for the first time, enabling element-resolved angular
anisotropy investigations. In non-centrosymmetric LiNbO, elemental
contributions by lithium and niobium are clearly distinguished by energy
dependent XUV-SHG measurements. This element-resolved and symmetry-sensitive
experiment suggests that the displacement of Li ions in LiNbO, which is
known to lead to ferroelectricity, is accompanied by distortions to the Nb ion
environment that breaks the inversion symmetry of the NbO octahedron as
well. Our simulations show that the measured second harmonic spectrum is
consistent with Li ion displacements from the centrosymmetric position by
0.5 Angstrom while the Nb-O bonds are elongated/contracted by
displacements of the O atoms by 0.1 Angstrom. In addition, the
polarization-resolved measurement of XUV-SHG shows excellent agreement with
numerical predictions based on dipole-induced SHG commonly used in the optical
wavelengths. This constitutes the first verification of the dipole-based SHG
model in the XUV regime. The findings of this work pave the way for future
angle and time-resolved XUV-SHG studies with elemental specificity in condensed
matter systems
Recommended from our members
Polarization-Resolved Extreme Ultraviolet Second Harmonic Generation from LiNbO
Second harmonic generation (SHG) spectroscopy ubiquitously enables the
investigation of surface chemistry, interfacial chemistry as well as symmetry
properties in solids. Polarization-resolved SHG spectroscopy in the visible to
infrared regime is regularly used to investigate electronic and magnetic orders
through their angular anisotropies within the crystal structure. However, the
increasing complexity of novel materials and emerging phenomena hamper the
interpretation of experiments solely based on the investigation of hybridized
valence states. Here, polarization-resolved SHG in the extreme ultraviolet
(XUV-SHG) is demonstrated for the first time, enabling element-resolved angular
anisotropy investigations. In non-centrosymmetric LiNbO, elemental
contributions by lithium and niobium are clearly distinguished by energy
dependent XUV-SHG measurements. This element-resolved and symmetry-sensitive
experiment suggests that the displacement of Li ions in LiNbO, which is
known to lead to ferroelectricity, is accompanied by distortions to the Nb ion
environment that breaks the inversion symmetry of the NbO octahedron as
well. Our simulations show that the measured second harmonic spectrum is
consistent with Li ion displacements from the centrosymmetric position by
0.5 Angstrom while the Nb-O bonds are elongated/contracted by
displacements of the O atoms by 0.1 Angstrom. In addition, the
polarization-resolved measurement of XUV-SHG shows excellent agreement with
numerical predictions based on dipole-induced SHG commonly used in the optical
wavelengths. This constitutes the first verification of the dipole-based SHG
model in the XUV regime. The findings of this work pave the way for future
angle and time-resolved XUV-SHG studies with elemental specificity in condensed
matter systems
Extreme Ultraviolet Second Harmonic Generation Spectroscopy in a Polar Metal.
The coexistence of ferroelectricity and metallicity seems paradoxical, since the itinerant electrons in metals should screen the long-range dipole interactions necessary for dipole ordering. The recent discovery of the polar metal LiOsO3 was therefore surprising [as discussed earlier in Y. Shi et al., Nat. Mater. 2013, 12, 1024]. It is thought that the coordination preferences of the Li play a key role in stabilizing the LiOsO3 polar metal phase, but an investigation from the combined viewpoints of core-state specificity and symmetry has yet to be done. Here, we apply the novel technique of extreme ultraviolet second harmonic generation (XUV-SHG) and find a sensitivity to the broken inversion symmetry in the polar metal phase of LiOsO3 with an enhanced feature above the Li K-edge that reflects the degree of Li atom displacement as corroborated by density functional theory calculations. These results pave the way for time-resolved probing of symmetry-breaking structural phase transitions on femtosecond time scales with element specificity
Recommended from our members
Extreme Ultraviolet Second Harmonic Generation Spectroscopy in a Polar Metal.
The coexistence of ferroelectricity and metallicity seems paradoxical, since the itinerant electrons in metals should screen the long-range dipole interactions necessary for dipole ordering. The recent discovery of the polar metal LiOsO3 was therefore surprising [as discussed earlier in Y. Shi et al., Nat. Mater. 2013, 12, 1024]. It is thought that the coordination preferences of the Li play a key role in stabilizing the LiOsO3 polar metal phase, but an investigation from the combined viewpoints of core-state specificity and symmetry has yet to be done. Here, we apply the novel technique of extreme ultraviolet second harmonic generation (XUV-SHG) and find a sensitivity to the broken inversion symmetry in the polar metal phase of LiOsO3 with an enhanced feature above the Li K-edge that reflects the degree of Li atom displacement as corroborated by density functional theory calculations. These results pave the way for time-resolved probing of symmetry-breaking structural phase transitions on femtosecond time scales with element specificity
Recommended from our members
Probing lithium mobility at a solid electrolyte surface
Solid-state electrolytes overcome many challenges of present-day lithium ion batteries, such as safety hazards and dendrite formation1,2. However, detailed understanding of the involved lithium dynamics is missing due to a lack of in operando measurements with chemical and interfacial specificity. Here we investigate a prototypical solid-state electrolyte using linear and nonlinear extreme-ultraviolet spectroscopies. Leveraging the surface sensitivity of extreme-ultraviolet-second-harmonic-generation spectroscopy, we obtained a direct spectral signature of surface lithium ions, showing a distinct blueshift relative to bulk absorption spectra. First-principles simulations attributed the shift to transitions from the lithium 1 s state to hybridized Li-s/Ti-d orbitals at the surface. Our calculations further suggest a reduction in lithium interfacial mobility due to suppressed low-frequency rattling modes, which is the fundamental origin of the large interfacial resistance in this material. Our findings pave the way for new optimization strategies to develop these electrochemical devices via interfacial engineering of lithium ions